Use clones, characterized cell lines biochemically transformed by HSV-2 and HSV-1 to form human-mouse somatic cell hybrids. Select for hybrid cells using suitable selective media. Analyze subclones of the somatic cell hybrids to verify the presence of herpes virus TK in the hybrid cells. Correlate the presence of individual human chromosomes in clonal sublines of hybrid cells with the presence of HSV-specified TK. Conduct biochemical tests for the presence of human isozymes to complement the karylogical identification of human chromosomesin hybrid subclones.